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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!news.mel.connect.com.au!munnari.OZ.AU!news.ecn.uoknor.edu!news.wildstar.net!news.ececs.uc.edu!newsfeeds.sol.net!news.maxwell.syr.edu!news.mathworks.com!uunet!in3.uu.net!192.244.176.52!news.iij.ad.jp!news.CET.CO.JP!usenet From: Michael Hancock <michaelh@cet.co.jp> Newsgroups: comp.programming.threads,comp.unix.bsd.freebsd.misc Subject: Re: [??] pure kernel vs. dual concurrency implementations Date: Tue, 25 Feb 1997 11:02:05 -0800 Organization: CET Lines: 32 Message-ID: <3313372D.1849@cet.co.jp> References: <330CE6A4.63B0@cet.co.jp> <874tf7lbxc.fsf@serpentine.com> NNTP-Posting-Host: chaos.cet.co.jp Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.01 (WinNT; I) Xref: euryale.cc.adfa.oz.au comp.programming.threads:3298 comp.unix.bsd.freebsd.misc:36059 Bryan O'Sullivan wrote: > m> Pure kernel proponents say that in the time all that was done a new > m> kernel thread could have been switched in. > > This is probably true. There are a few points to note, though: > > - Scheduler activations, or upcalls, only need to be performed when > your process is not running at a "reasonable" concurrency level > > - This means that for most programs, you only have paths through the > kernel occasionally, versus at every context switch for pure kernel > threads > > - The overhead of deciding when to make an upcall and performing the > upcall itself should not be significantly greater than that of > switching kernel-supprted threads When would scheduler activations occur? 1) When the current thread in a multi-threaded process blocks before it's quantum is used up? 2) When the VP's are underutilized? Also, who gets priority, runnable single-threaded processes or a runnable thread in a multi-threaded process? Regards, Mike Hancock